LXR linux/arch/x86/mm/kasan_init

   1#define DISABLE_BRANCH_PROFILING
   2#define pr_fmt(fmt) "kasan: " fmt
   3#include <linux/bootmem.h>
   4#include <linux/kasan.h>
   5#include <linux/kdebug.h>
   6#include <linux/mm.h>
   7#include <linux/sched.h>
   8#include <linux/sched/task.h>
   9#include <linux/vmalloc.h>
  10
  11#include <asm/e820/types.h>
  12#include <asm/tlbflush.h>
  13#include <asm/sections.h>
  14
  15extern pgd_t early_level4_pgt[PTRS_PER_PGD];
  16extern struct range pfn_mapped[E820_MAX_ENTRIES];
  17
  18static int __init map_range(struct range *range)
  19{
  20        unsigned long start;
  21        unsigned long end;
  22
  23        start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
  24        end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));
  25
  26        /*
  27         * end + 1 here is intentional. We check several shadow bytes in advance
  28         * to slightly speed up fastpath. In some rare cases we could cross
  29         * boundary of mapped shadow, so we just map some more here.
  30         */
  31        return vmemmap_populate(start, end + 1, NUMA_NO_NODE);
  32}
  33
  34static void __init clear_pgds(unsigned long start,
  35                        unsigned long end)
  36{
  37        pgd_t *pgd;
  38
  39        for (; start < end; start += PGDIR_SIZE) {
  40                pgd = pgd_offset_k(start);
  41                /*
  42                 * With folded p4d, pgd_clear() is nop, use p4d_clear()
  43                 * instead.
  44                 */
  45                if (CONFIG_PGTABLE_LEVELS < 5)
  46                        p4d_clear(p4d_offset(pgd, start));
  47                else
  48                        pgd_clear(pgd);
  49        }
  50}
  51
  52static void __init kasan_map_early_shadow(pgd_t *pgd)
  53{
  54        int i;
  55        unsigned long start = KASAN_SHADOW_START;
  56        unsigned long end = KASAN_SHADOW_END;
  57
  58        for (i = pgd_index(start); start < end; i++) {
  59                switch (CONFIG_PGTABLE_LEVELS) {
  60                case 4:
  61                        pgd[i] = __pgd(__pa_nodebug(kasan_zero_pud) |
  62                                        _KERNPG_TABLE);
  63                        break;
  64                case 5:
  65                        pgd[i] = __pgd(__pa_nodebug(kasan_zero_p4d) |
  66                                        _KERNPG_TABLE);
  67                        break;
  68                default:
  69                        BUILD_BUG();
  70                }
  71                start += PGDIR_SIZE;
  72        }
  73}
  74
  75#ifdef CONFIG_KASAN_INLINE
  76static int kasan_die_handler(struct notifier_block *self,
  77                             unsigned long val,
  78                             void *data)
  79{
  80        if (val == DIE_GPF) {
  81                pr_emerg("CONFIG_KASAN_INLINE enabled\n");
  82                pr_emerg("GPF could be caused by NULL-ptr deref or user memory access\n");
  83        }
  84        return NOTIFY_OK;
  85}
  86
  87static struct notifier_block kasan_die_notifier = {
  88        .notifier_call = kasan_die_handler,
  89};
  90#endif
  91
  92void __init kasan_early_init(void)
  93{
  94        int i;
  95        pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
  96        pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
  97        pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
  98        p4dval_t p4d_val = __pa_nodebug(kasan_zero_pud) | _KERNPG_TABLE;
  99
 100        for (i = 0; i < PTRS_PER_PTE; i++)
 101                kasan_zero_pte[i] = __pte(pte_val);
 102
 103        for (i = 0; i < PTRS_PER_PMD; i++)
 104                kasan_zero_pmd[i] = __pmd(pmd_val);
 105
 106        for (i = 0; i < PTRS_PER_PUD; i++)
 107                kasan_zero_pud[i] = __pud(pud_val);
 108
 109        for (i = 0; CONFIG_PGTABLE_LEVELS >= 5 && i < PTRS_PER_P4D; i++)
 110                kasan_zero_p4d[i] = __p4d(p4d_val);
 111
 112        kasan_map_early_shadow(early_level4_pgt);
 113        kasan_map_early_shadow(init_level4_pgt);
 114}
 115
 116void __init kasan_init(void)
 117{
 118        int i;
 119
 120#ifdef CONFIG_KASAN_INLINE
 121        register_die_notifier(&kasan_die_notifier);
 122#endif
 123
 124        memcpy(early_level4_pgt, init_level4_pgt, sizeof(early_level4_pgt));
 125        load_cr3(early_level4_pgt);
 126        __flush_tlb_all();
 127
 128        clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 129
 130        kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 131                        kasan_mem_to_shadow((void *)PAGE_OFFSET));
 132
 133        for (i = 0; i < E820_MAX_ENTRIES; i++) {
 134                if (pfn_mapped[i].end == 0)
 135                        break;
 136
 137                if (map_range(&pfn_mapped[i]))
 138                        panic("kasan: unable to allocate shadow!");
 139        }
 140        kasan_populate_zero_shadow(
 141                kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
 142                kasan_mem_to_shadow((void *)__START_KERNEL_map));
 143
 144        vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
 145                        (unsigned long)kasan_mem_to_shadow(_end),
 146                        NUMA_NO_NODE);
 147
 148        kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
 149                        (void *)KASAN_SHADOW_END);
 150
 151        load_cr3(init_level4_pgt);
 152        __flush_tlb_all();
 153
 154        /*
 155         * kasan_zero_page has been used as early shadow memory, thus it may
 156         * contain some garbage. Now we can clear and write protect it, since
 157         * after the TLB flush no one should write to it.
 158         */
 159        memset(kasan_zero_page, 0, PAGE_SIZE);
 160        for (i = 0; i < PTRS_PER_PTE; i++) {
 161                pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO);
 162                set_pte(&kasan_zero_pte[i], pte);
 163        }
 164        /* Flush TLBs again to be sure that write protection applied. */
 165        __flush_tlb_all();
 166
 167        init_task.kasan_depth = 0;
 168        pr_info("KernelAddressSanitizer initialized\n");
 169}
 170